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- What is Rebar?
- Types of Steel Reinforcement Bars
- 1. Mild Steel Bar
- 2. Deformed Steel Bar
- 3. Other Types of Rebars
What is Rebar?Steel reinforcement bars or rebars are used to improve the tensile strength of the concrete, since concrete is very weak in tension, but is strong in compression. Steel is only used as rebar because elongation of steel due to high temperatures (thermal expansion coefficient) nearly equals to that of concrete.
Grades of Rebar in Different CodesTable 1: Grades of Rebar in Different Codes
|American Standard (ASTM A 615)||Euro Standard(DIN 488)||British Standard BS4449: 1997||Indian Standard (IS: 1786)|
|Grade 75 (520)||BST 500 S||GR 460 A||Grade Fe – 415, Fe – 500, Fe – 500D|
|Grade 80 (550)||BST 500 M||GR 460 B||Grade Fe – 550|
Types of Steel Reinforcement Bars
1. Mild Steel BarThe surface of the mild steel bars are plain and round in shape. They are available in various sizes of 6 mm to 50 mm. They are used in concrete for special purposes, such as dowels at expansion joints, where bars must slide in a metal or paper sleeve, for contraction joints in roads and runways, and for column spirals. They are easy to cut and bend without damage.
For structural buildings like bridges and other heavy structures, mild steel bar is not recommended due to no great bonding between concrete and steel, slippage and strength.
Grades in mild steel bars
1. Mild Steel Bars
- Mild steel bars grade-I designated as Fe 410-S or Grade 60.
- Mild steel bars grade-II designated as Fe-410-o or Grade 40.
Physical Requirement of Mild Steel BarsTable 2:Physical Requirement of Mild Steel Bars
|Types of Nominal size of bar||Ultimate Tensile Stress in N/mm2||Yield Stress N/mm2||Elongation Percentage min|
|Mild Steel Grade I or Grade 60|
|For Bars upto 20mm||410||250||23|
|For Bars above 20mm upto 50mm||410||240||23|
|Mild Steel Grade II or Grade 40|
|For Bars upto 20mm||370||225||23|
|For Bars above 20mm upto 50mm||370||215||23|
|Medium Tensile Steel Grade -75|
|For Bars upto 16mm||540||350||20|
|For Bars above 16mm upto 32mm||540||340||20|
|For Bars above 32mm upto 50mm||510||330||20|
2. Deformed Steel Bar
Deformed steel bars have ribs, lugs and indentation on the surface of the bar, which reduces the major problem that is faced by mild steel bar due to slippage and good bonding is achieved between concrete and rebar. The tensile properties is higher compared to other rebars. These bars are produced in sections from 6 mm to 50 mm dia.
Types of Deformed Steel Bars
1. TMT Bars (Thermo Mechanically Treated Bars)
Thermo Mechanically Treated Bars are hot treated bars that are high in strength used in reinforced cement concrete (RCC) work. It is the latest induction in the MS steel bars with superior properties such as strength, ductility, welding ability, bending ability and highest quality standards at international level.
Characteristics of TMT Rebars
- Better ductility and malleability
- High yield strength and toughness
- More bonding strength
- Earthquake resistance
- Corrosion resistance
- High thermal resistance
- Economical and safe in use
- No loss in strength at welded joints
- Ordinary electrodes used for welding the joints
2. High Strength Deformed BarsHigh strength deformed bars are cold twisted steel bars with lugs, ribs, projection or deformation on the surface. It the extensively and majorly used for reinforcement purposes in a construction. These bars are produced in sizes or sections from 4 mm to 50 mm in diameter.
Characteristics of HSD Rebar
- Low carbon value - HSD Bars have lower carbon level, resulting in good ductility, strength and welding ability.
- Superior bonding strength - HSD bars are well known for their excellent bonding strength when used with concrete.
- Welding capability - Since these bars have lower carbon content, they have 100% welding capability than conventional bars.
- High tensile strength - HSD bars feature high tensile strength. They offer great asset in construction process, where a lot of bending and re bending is required.
- Wide application range - These bars have wide application range like in building residential, commercial and industrial structures, bridges, etc.
- Satisfactorily malleability - Minimum weight and maximum strength and suitable for both compression and tension reinforcement.
3. Other Types of Rebars
Depending upon the type of material used in the production of rebar, different types of rebars are